Hopefully, it’s not a surprise to you that dogs, like humans, have two eyes. (They do.) What many dog owners wonder about is what do dogs can actually see, and how they see as well (besides the obvious answer of opening their eyes). Do they see the world differently than we do? Do their eyes work as well, better or worse than ours? Is there any difference in the way they function and do dogs, like humans, have similar vision problems?
In this article, we’ll try to answer all of those questions so that you can clearly see the answer and have a better idea of how the world looks to your dearest doggie bud. Enjoy.
How Does Canine Vision Work?
Even though their eyes look similar to ours, a dog sees the world quite differently than a human. The main reason for the difference is due to the 2 types of light receptors that both dogs and humans have in their eyes. These 2 light receptors are called cones and rods and each has a different function.
- Cones help both dogs and humans to differentiate between different colors; red, green and blue (and all the colors that are ‘made’ with these 3.
- Rods help both dogs and humans see things when there’s low or little light
The difference between your canine companion’s eyes and yours? First, humans have more cones and can detect, as we mentioned, 3 colors, while dogs have fewer cones and can detect only 2 colors. Interestingly, scientists haven’t yet discovered which colors it is that dogs can see, although they speculate that it’s blue and yellow.
Second, dogs have more rods, which enables them to see better than humans at night or when there’s less light. Extra rods are also the reason that, at night, dogs’ eyes shine and look ‘eerie’. Dogs also have something called the tapetum lucidum, a layer of tissue that reflects incoming light into their retinas. And all three of these differences put to rest the old fallacy that dogs only see in black and white.
Lastly, according to Dr. Michale H. Brown, a veterinary opthalmologist who tends to his canine patients at Animal Eyes of New Jersey, dogs’ eyes are “not as highly adapted, so their color spectrum is not vivid or broad” as humans.
Are Dogs Color Blind and What Colors Do they See, If Any?
Dogs are definitely not color blind, a myth we just busted a couple of sentences ago. Although they see fewer colors than humans because their eyes have fewer cones, they can see at least 2 colors (besides black, white and gray) and likely a couple more. As we mentioned previously, scientists really aren’t sure of the actual colors that dogs can see, although they believe that they are the colors yellow and blue. The possibility that they can see the color purple is also high.
Can Dogs be Nearsighted or Farsighted?
It’s possible that a dog could be either nearsighted or farsighted but it’s also very unlikely. There are, however, several breeds of dogs that do have problems with either one problem or the other, which we’ll talk about in just a minute.
Some scientists will tell you that, technically, all dogs are nearsighted. However, as all dogs have the same challenge seeing things far away, and all dogs have adapted their other senses to make up for this lack of being able to see over long distances, most agree that this isn’t nearsightedness at all but simply the way dogs see.
Do Dogs With 2 Different Eye Colors Have Visions Problems?
When a dog has 2 eyes of a different color, a natural phenomenon called heterochromia, the problem does not affect their eyes (except to make them look amazing). Interestingly, when a dog is born with one blue eye and one brown eye they can sometimes be deaf, as this occasionally occurs when a dog is an albino.
What Makes Up a Dogs Eye (and is it Similar to Humans)?
Dogs’ eyes are quite similar to human eyes although, as we mentioned before, they have fewer cones and more rods. This difference helps them to see better in the dark but reduces the number of colors that they can see. Just as humans do a dogs’ eyes have a cornea, retina, lens, pupil and the aforementioned rods and cones.
Dogs also, as mentioned above, have a layer of tissue that reflects incoming light into their retinas called the tapetum lucidum. One other fascinating extra part that dogs have and humans don’t is called a nictitating membrane, which is essentially a third eyelid. It’s located between the globe of the eye (eyeball) and the lower eyelid. Scientists believe that this membrane protects their eyes from debris. It’s usually not visible unless a dog, especially an English Bulldog, has certain afflictions (cherry eye for one) or their eye has been irritated by a foreign object.
What Shapes are Dogs Eyes?
Dogs can have several eye shapes, just like humans, including prominent, oval, circular and almond-shaped eyes. There are a few others as well, including;
- Haw Eyes- This is when the 3rd eyelid, the nictitating membrane, is very prominent. It’s seen mostly in Bloodhounds and St. Bernards.
- China Eyes- This is more an eye color than a shape. It’s when a dog has a clear blue eye speckled with light blue or white
- Prominent Eyes- Sometimes called ‘bug eyes’, these are found mostly on Pugs
- Triangular Eyes- A tent-shaped eye that appears to have 3 corners, these are found in Afghan Hounds
How Fast Do Dogs Process What they See?
Generally speaking, dogs process what they see as quickly as humans although what they perceive and how they understand what they see is much different than humans. Their fewer cones and a greater amount of rods aside, what your dog sees goes to its brain and registers as quickly as what we humans see, so almost instantaneously. (Where dogs really outgun humans, so to speak, is with their amazing noses and sense of smell, but that’s a tale for another day.)
Do Dogs Have Better Peripheral Vision than Humans?
As a matter of fact, yes, they do! This is one of the reasons that dogs are such great hunters because, like humans, they can see things to their sides even if they aren’t looking directly at them. Dogs are even better than humans at this, with a wider field of vision than we have, about 250 degrees compared to our 180 degrees. One reason for this is that dog eyes are set further apart than human eyes, allowing them to see things that a human would have to turn their head quite far to see.
Which Breeds of Dogs Have the Best and the Worst Vision?
If you’ve ever wondered why Greyhounds are used to race, it’s because of their terrific eyesight. While we don’t condone dog racing the fact is that Greyhounds chase an electric rabbit which has no smell at all, because they can see better than most other dogs. These types of dogs are called ‘sighthounds’ because they hunt almost purely using their eyesight rather than their sense of smell. Other dogs that see quite well include;
Breeds with the best vision
- Afghan Hound
- Italian Greyhound
- Irish Wolfhound
- Scottish Deerhound
Breed that have the poorest vision
- English Springer Spaniel
- Siberian Husky
- Boston Terrier
- Lhasa Apso
- Great Dane
What Are Some Common Vision Problems in Dogs?
Although dogs can’t read eye charts or wear glasses they do suffer from a variety of vision problems, some of which are due to the breed and others which are brought about by aging (just like we humans). Below are 7 of the most common vision problems in dogs in alphabetical order.
- Blepharospasm- Red, swollen and sometimes closed eyelids due to involuntary contraction and rapid blinking
- Cataracts- This is when the lens goes from clear to opaque and affects vision
- Cherry Eye- This is when the nictitating membrane, their 3rd eyelid, pops out. Commonly known as ‘cherry eye’
- Conjunctivitis- Inflammation of the inner mucous membrane (the conjunctiva)
- Dry Eye/Keratoconjunctivitis Sicca (KCS)- This is known as dry-eye syndrome and is caused by a variety of problems including drug toxicity, dry nose, systemic disease or a neurogenic problem
- Entropion- When a dog’s eyelid rolls inward
- Glaucoma- An imbalance in the pressure of the eye that usually affects older dogs
Can A Dogs Eyes Tell You About Their Health?
Yes, they can. For example, if the whites of their eyes are yellowed they might be suffering from severe liver disease. This yellowing is called jaundice and is seen in humans as well. If their pupils are different sizes it might indicate that they have had some type of head trauma. Cancer and diabetes in dogs will cause their eyes to become cloudy due to extra protein or white blood cells. Lastly, a very pale sclera, which is the outer layer of the eye and is usually bright white, can be caused by abdominal bleeding or kidney disease.
As you can see, the facts about your dog’s eyes are quite fascinating. Like humans, their eyes are also vitally important and can tell you things about your pupper that they can’t tell you themselves. And, of course, they’re wonderful for staring down deep into your very soul.